// services/shortStockAlertStore.js
// Independent, fully automated feature (NOT tied to the Inventory Status
// Report screen at all): admin defines a watch-list of item codes/item
// groups in System Settings, each with its own concerned-user recipients.
// A background job (started from server.js, see checkShortStock() below)
// periodically sums each watched item's on-hand quantity (OITW.OnHand,
// across every warehouse) and emails the concerned users the FIRST time it
// hits zero — not on every check while it stays at zero, and not gated by
// the stage-change notification system (services/notifyStore.js) at all,
// since this isn't a workflow-stage event.
'use strict';
const sql = require('mssql');
const appSettings = require('./appSettingsStore');
const hanaUsers = require('./hanaUsers');
const mailer = require('./mailer');
const { getPool: getSapPool } = require('./sqlPool');

const TABLE = `[dbo].[ZSHORT_STOCK_STATE]`;

let _conn = null;
async function getConn() {
  if (_conn) return _conn;
  _conn = await sql.connect({
    server: process.env.APP_SQL_HOST,
    port: parseInt(process.env.APP_SQL_PORT),
    user: process.env.APP_SQL_USER,
    password: process.env.APP_SQL_PASSWORD,
    database: process.env.APP_SQL_DATABASE,
    options: { encrypt: true, trustServerCertificate: true },
  });
  return _conn;
}
async function exec(sqlQuery, params = []) {
  const conn = await getConn();
  const request = conn.request();
  params.forEach((param, index) => { request.input(`param${index}`, param); });
  const replacedSql = sqlQuery.replace(/\?/g, (m, offset, string) => {
    const i = (string.slice(0, offset).match(/\?/g) || []).length;
    return `@param${i}`;
  });
  const result = await request.query(replacedSql);
  return result.recordset || [];
}
function isAlreadyExists(e) {
  const m = (e.message || '').toLowerCase();
  return m.includes('already exists') || m.includes('there is already an object');
}

async function bootstrap() {
  console.log('[SHORT-STOCK-ALERT] Checking table', TABLE, '...');
  await exec(`
    CREATE TABLE ${TABLE} (
      ITEM_CODE     NVARCHAR(60) NOT NULL,
      COMPANY       NVARCHAR(60) NOT NULL,
      WAS_ZERO      BIT DEFAULT 0,
      LAST_ALERT_AT DATETIME2,
      CONSTRAINT PK_SHORT_STOCK_STATE PRIMARY KEY (ITEM_CODE, COMPANY)
    )
  `).catch(e => { if (!isAlreadyExists(e)) throw e; });
  console.log('[SHORT-STOCK-ALERT] ✅ Ready');
}

function esc(s) { return String(s == null ? '' : s).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;'); }

// Resolves every configured rule into a flat map of itemCode → Set of
// recipient usernames (a item matched by more than one rule — e.g. both a
// direct ITEM rule and a GROUP rule it happens to belong to — gets every
// rule's recipients merged, mailed once).
async function resolveWatchedItems(company) {
  const rules = appSettings.shortStockAlertRules();
  const map = new Map(); // itemCode -> Set(usernames)
  if (!rules.length) return map;

  const itemRules = rules.filter(r => r.type === 'ITEM' && r.value);
  const groupRules = rules.filter(r => r.type === 'GROUP' && r.value);

  itemRules.forEach(r => {
    const set = map.get(r.value) || new Set();
    (r.recipients || []).forEach(u => set.add(u));
    map.set(r.value, set);
  });

  if (groupRules.length) {
    const pool = await getSapPool(company);
    for (const r of groupRules) {
      const grp = parseInt(r.value);
      if (isNaN(grp)) continue;
      try {
        const rows = await pool.request().query(`SELECT "ItemCode" FROM [dbo].[OITM] WHERE "ItmsGrpCod"=${grp}`);
        rows.recordset.forEach(row => {
          const set = map.get(row.ItemCode) || new Set();
          (r.recipients || []).forEach(u => set.add(u));
          map.set(row.ItemCode, set);
        });
      } catch (e) { console.warn('[SHORT-STOCK-ALERT] group resolve failed for', r.value, e.message); }
    }
  }
  return map;
}

async function getState(itemCode, company) {
  const rows = await exec(`SELECT * FROM ${TABLE} WHERE ITEM_CODE=? AND COMPANY=?`, [itemCode, company]);
  return rows[0] || null;
}
async function upsertState(itemCode, company, wasZero, alertedNow) {
  const existing = await getState(itemCode, company);
  const now = new Date().toISOString().replace('T', ' ').replace('Z', '').substring(0, 23);
  if (existing) {
    await exec(
      `UPDATE ${TABLE} SET WAS_ZERO=?${alertedNow ? ', LAST_ALERT_AT=?' : ''} WHERE ITEM_CODE=? AND COMPANY=?`,
      alertedNow ? [wasZero ? 1 : 0, now, itemCode, company] : [wasZero ? 1 : 0, itemCode, company]
    );
  } else {
    await exec(
      `INSERT INTO ${TABLE} (ITEM_CODE, COMPANY, WAS_ZERO, LAST_ALERT_AT) VALUES (?,?,?,?)`,
      [itemCode, company, wasZero ? 1 : 0, alertedNow ? now : null]
    );
  }
}

async function sendShortStockMail(itemCode, itemName, recipients, company) {
  const all = await hanaUsers.listUsers();
  const want = new Set([...recipients].map(u => u.toLowerCase()));
  const users = all.filter(u => u.active && u.emailNotify !== false && want.has((u.username || '').toLowerCase()) && u.email);
  if (!users.length) return false;
  const html = `<div style="font-family:Segoe UI,Arial,sans-serif;max-width:520px">
    <h2 style="margin:0 0 12px;font-size:16px;color:#1a2b4a">⚠ Out of Stock — ${esc(itemCode)}</h2>
    <table>
      <tr><td style="padding:3px 10px 3px 0;color:#667;font-size:13px">Item Code</td><td style="padding:3px 0;font-size:13px;font-weight:600">${esc(itemCode)}</td></tr>
      <tr><td style="padding:3px 10px 3px 0;color:#667;font-size:13px">Description</td><td style="padding:3px 0;font-size:13px;font-weight:600">${esc(itemName)}</td></tr>
      <tr><td style="padding:3px 10px 3px 0;color:#667;font-size:13px">Company</td><td style="padding:3px 0;font-size:13px;font-weight:600">${esc(company)}</td></tr>
      <tr><td style="padding:3px 10px 3px 0;color:#667;font-size:13px">In Stock</td><td style="padding:3px 0;font-size:13px;font-weight:600;color:#e53e3e">0</td></tr>
    </table>
    <p style="margin-top:20px;color:#98a;font-size:11px">Automated alert from the SAP ERP Portal — Short in Stock watch-list (Admin → System Settings).</p>
  </div>`;
  return mailer.sendMail({ to: users.map(u => u.email), subject: `Out of Stock — ${itemCode}${itemName ? ' (' + itemName + ')' : ''}`, html });
}

// Main job — safe to call on a timer; never throws (a failure here must
// never crash the app), logs and returns instead.
async function checkShortStock() {
  try {
    if (!appSettings.shortStockAlertEnabled()) return;
    const company = process.env.SAP_B1_COMPANY;
    if (!company) return;
    const watched = await resolveWatchedItems(company);
    if (!watched.size) return;

    const itemCodes = [...watched.keys()];
    const pool = await getSapPool(company);
    const list = itemCodes.map(c => `'${String(c).replace(/'/g, "''")}'`).join(',');
    const rows = await pool.request().query(`
      SELECT T0."ItemCode", T0."ItemName", SUM(ISNULL(T1."OnHand",0)) AS "InStock"
      FROM [dbo].[OITM] T0
      LEFT JOIN [dbo].[OITW] T1 ON T1."ItemCode"=T0."ItemCode"
      WHERE T0."ItemCode" IN (${list})
      GROUP BY T0."ItemCode", T0."ItemName"`);

    for (const row of rows.recordset) {
      const itemCode = row.ItemCode;
      const inStock = Number(row.InStock) || 0;
      const state = await getState(itemCode, company);
      const wasZero = !!(state && state.WAS_ZERO);
      const isZero = inStock <= 0;
      if (isZero && !wasZero) {
        const sent = await sendShortStockMail(itemCode, row.ItemName, watched.get(itemCode), company);
        console.log(`[SHORT-STOCK-ALERT] ${itemCode} hit zero — mail ${sent ? 'sent' : 'skipped (SMTP not configured / no eligible recipients)'}`);
        await upsertState(itemCode, company, true, true);
      } else if (!isZero && wasZero) {
        await upsertState(itemCode, company, false, false);
      }
    }
  } catch (e) {
    console.error('[SHORT-STOCK-ALERT] check failed:', e.message);
  }
}

module.exports = { bootstrap, checkShortStock, resolveWatchedItems };